Dr. Eto described his study of 9 obese – but not diabetic – subjects with a mean body mass index 27 k/m2 (in Japan, obesity begins at a BMI of 25 kg/m2). At baseline, the volunteers’ mean fasting plasma glucose was 99 mg/dL. They all ate the same 630-calorie meal on two separate days: bread, butter, a hard-boiled egg, steamed vegetables, a banana, and milk.

On day one, they had to finish it in 20 minutes, chewing each bite 5 times. On the second test day, they ate the same meal, also in 20 minutes, but chewed each mouthful 30 times.

Dr. Eto and his colleagues measured two satiety hormones – glucagon-like peptide (GKP-1) and peptide YY (PYY) before and after each meal.

The results will please grandmas worldwide.

Chewing each bite 30 times significantly increased the levels of both hormones over chewing 5 times, said Dr. Eto of Ohu University, Fukushima, Japan.

Among the 5-chew gulpers, plasma PYY increased from 36 pg/mL to 41 pg/mL – not a significant change. But the slow chewers had quite a different outcome. “The 30-times chewing group had a significant increase in plasma PYY,” Dr. Eto said. Their levels jumped from a mean of 36 pg/mL to 66 pg/mL.

The story was repeated with GLP-1. The fast-chewers did have an increase – although not significant (5 pmol/L to 17 pmol/L). But the slow-chewers had much better results, increasing their GLP-1 from 5 pmol/L to a whopping 29 pmol/L.

“This is the first report that thorough chewing stimulates postprandial increases in the two hormones,” Dr. Eto said. “These hormones reduce appetite and food consumption, so thorough chewing may help obese subjects to lose weight.”

Besides, he said, Japanese grandmothers “since the old days” have advised kids to do a lot of chewing. So much so, he added, that the Japanese government has issued a recommendation to chew each bite of food 30 times – to help avert the country’s growing obesity problem. “That is why we picked 30 times chewing,” for the study, Dr. Eto said.

Some audience members weren’t completely convinced that the good results are related to the combination of chewing and food intake. One questioned whether the mechanics of chewing was key benefit, stimulating the vagusl nerve to release GLP-1. “For instance,” he asked, “what if the subjects chewed the food and then spat it out? What would the results be then?”

To which moderator Dr. Davide Carvalho replied, “I believe chewing and spitting out the food could be the best diet we could invent.”